Drone.ci is treating GDPR like any other law by steering well clear of the territory it regulates. The US also has stringent rules about online gambling, payment processing, pornography, copyrighted material, etc. Normal website operators don't become familiar with these rules or how to thread a business through them. They simply don't engage in regulated activity at all, unless making a deliberate and well-capitalized entrance with the help of lawyers and compliance professionals. (Obviously there are some high-profile counterexamples, but those are, well, high-profile).
If the GDPR were a law about data brokerage or advertising, then forum operators would be similarly far away from it. But it's a law about the handling and storage of data related to people, which you definitely do if you're running a forum. Ordinary websites have never been that close to the boundaries of legality before, so people are scared.
As if he read all laws of his own country that apply to him. Raise your hand if you actually read and comprehend all laws that apply to you. I'm willing to bet there's not a single person on this planet who really reads and comprehends all laws completely.
Usually you just go with common sense and reading a blog post or two when it seems relevant: that usually makes compliant and in the worst case it will get you a warning from the regulator (they give warnings for unintentional first-time violations, so they'll tell you if you're doing wrong and it bothers them enough (usually you're too small anyway), and you get a chance to improve).